DE102009047960A1 - Apparatus and method for optimizing exhaust temperature control in a vehicle during particulate filter regeneration - Google Patents

Abstract

One method controls exhaust temperature of a vehicle engine during regeneration of a particulate filter (PF) in a vehicle having an oxidation catalyst (OC) and a selective catalytic reduction (SCR) catalyst. The method ensures that an OC end temperature does not exceed a maximum OC outlet setpoint temperature and a calibrated OC outlet maximum temperature. An apparatus for controlling a temperature of the exhaust gas includes sensors for measuring a temperature in the exhaust system and a controller having an algorithm, a look-up table of OC temperatures, and a look-up table of PF temperatures. The algorithm calculates an OC outlet setpoint temperature using the look-up tables and a delayed error value that balances a thermal mass of the SCR. The actual OC outlet temperature is limited during regeneration of the PF to the lower value of OC outlet setpoint temperature and a calibrated OC outlet maximum temperature.

Description

Technical area

The The present invention relates to a system and a method for Controlling the temperature of an exhaust gas in a vehicle during a Regeneration of a particle filter.

Background of the invention

In one by an internal combustion engine of the prior art known type driven vehicle can be a particulate filter in be positioned in the vehicle exhaust system to remove particulates, before the particulate matter can be expelled to the atmosphere. Such a particle filter can be more microscopic when picking up and holding back Particles of soot, Ash, sulphates, metal particles and / or any other particulate matter, that usually produced as a by-product of the fuel combustion process, be relatively efficient. While Diesel engines very common use such a filter, which is widely used as a diesel particulate filter or DPF is known certain gasoline engine designs, such as direct injection engines or DI (short for English Direct Injection) also a similar one Use particle filter. A highly efficient particulate filter can be independent of the fuel species clog relatively quickly if it has large particle amounts is exposed, whereby an increased differential pressure over the Particle filter is generated. To counteract this, the particle filter can be exchanged accordingly a predetermined maintenance cycle or can, more usual is to be regenerated to extend the life of the filter.

One Particulate filter, hereinafter abbreviated as PF for the sake of simplicity, can by burning or oxidizing the accumulated particulate material below Use of a catalyst can be regenerated. The regeneration process occurs when the temperature in the PF exceeds a threshold of about 450 degrees Celsius (° C) is raised. While PF regeneration becomes the temperature in the exhaust gas or exhaust stream raised to this threshold to the regeneration process to facilitate. A possibility, To achieve such a temperature increase, the benefits an oxidation catalyst (OC, abbreviated to the English Oxidation Catalyst) in conjunction with increased hydrocarbon loading in the stream from exhaust upstream of the PF.

In In the OC itself, a chemical process splits the increased hydrocarbons in relatively inert by-products or compounds. A typical one For example, OC can be palladium or various platinum catalysts use the hydrocarbon values by means of a simple To reduce oxidation process. This process is exothermic Nature, resulting in increased Exhaust gas temperature leads. At the outlet of the OC, a temperature sensor can be used, and The control of the outlet temperature can be done by adjusting the amount or the value of hydrocarbons introduced into the exhaust stream be achieved. This method of temperature control is in Generally sufficient if the inlet to the PF directly downstream of the OC outlet located. The same method of temperature control can but under certain circumstances, for example, if a relatively moderately large thermal mass between the OC outlet and the PF inlet is less optimal be.

Summary of the invention

Accordingly, become a method and apparatus for optimizing temperature control an exhaust gas or exhaust gas stream of a vehicle engine is provided. The device controls the temperature of the exhaust gas in the exhaust system while the regeneration of the particulate filter (PF). The device comprises the PF itself, an oxidation catalyst (OC) and a catalyst for selective catalytic Reduction or SCR (abbreviated to Selective Catalytic Reduction), which is between the OC and the PF in the exhaust stream. The SCR sees the above mentioned relatively large thermal Mass in front. The PF can selectively regenerate using the OC be, with the SCR for it is formed, nitrogen oxides or NOx gases in relatively inert or harmless To convert by-products. Using the method and the Systems of the invention are the appearance and / or the strength of a Temperature overshoot or a temperature fluctuation minimized. Analogously, all after-treatment components, d. H. Components or other devices that contain other gases or by-products downstream receive and / or treat the PF, before such a temperature overshoot adequately protected.

The exhaust system further includes a controller and a plurality of sensors each configured to measure a temperature in different regions or portions of the exhaust system, including downstream of the OC and upstream of the PF. The controller includes an algorithm and may also include an OC temperature lookup table and a PF temperature lookup table to determine a pair of temperature setpoints, as described below. Alternatively, if the look-up tables are not used, the device may utilize one or more curves and / or a scalar calibration function or other suitable function. The algorithm will to thereby calculate an OC outlet setpoint temperature using the data extracted from the look-up tables or otherwise from the alternative curve and / or function. The algorithm restricts the actual OC outlet temperature during regeneration of the PF to the lesser of a calculated OC outlet setpoint temperature and a calibrated OC outlet maximum temperature.

It Two control loops are used to control the temperature of the PF inlet. The primary Loop control variable is the outlet temperature of the OC. These certain loop controls by changing the concentration of Hydrocarbons in the exhaust gas, for example by using Means in the cylinders, an external hydrocarbon dosing device or other suitable method, the outlet temperature of the OC a predetermined or calibrated first "set point" of the temperature. The secondary control loop uses an additional one Temperature sensor connected to the outlet of the SCR or alternatively positioned at the inlet of the PF. The secondary control loop uses one second temperature setpoint, which is from a measured PF inlet temperature can be subtracted to thereby provide an error value or error term to calculate. The error term can then be filtered in a way or processed, which increases the system stability, before moving to the first Temperature setpoint is added. The temperature control on the Inlet of the PF is thereby optimized while being protected from temperature overshoot.

at Using the method and system of the invention will be two desirable or calibrated temperature setpoints determined: a first temperature setpoint for the OC outlet temperature and a second temperature setpoint for the PF inlet temperature. The exhaust gas temperature is first determined by the first temperature setpoint controlled and then you leave they stabilize, for example - but not exclusively - wait, until a predetermined interval has passed or a timer has expired. As soon as the exhaust gas temperature stabilizes, it will the calculated difference between a measured PF inlet temperature and its calibrated temperature setpoint. This value, hereinafter referred to as error term, may be referred to Need to be filtered to improve system stability, and then become back to the OC outlet temperature setpoint, i. H. the first temperature setpoint, added. This can reduce the concentration of hydrocarbons be adjusted indirectly in the exhaust stream to the temperature in to control the PF.

The The foregoing features and advantages as well as other features and advantages The present invention will be readily apparent from the following detailed Description of the best methods for carrying out the invention in connection with the accompanying drawings.

Brief description of the drawings

1 Figure 3 is a schematic illustration of a vehicle having an engine and an exhaust system controllable by the apparatus and method of the invention;

2 FIG. 4 is an illustrative or representative series of graphs illustrating an exemplary temperature relationship between an oxidation catalyst (OC) and particulate filter (PF) in the vehicle of FIG 1 describe; and

3 Figure 11 is a schematic representation of an information flow or control sequence according to the method of the invention.

Description of the preferred embodiments

Referring to the drawings, wherein like reference numerals designate like components throughout the several figures, and starting with FIG 1 includes a vehicle 10 a motor (E) 12 and a gearbox (T) 14 , The motor 12 is configured as a conventional internal combustion engine and is therefore for burning a supply of fuel 25 that came from a swamp or a tank 24 is sucked, usable. The fuel 25 may depend on the configuration of the engine 12 Be diesel or gasoline. The motor 12 indicates a regulator or throttle 70 on, as needed, depending on the position of the throttle 70 for admitting a predetermined amount or a predetermined percentage of the fuel 25 and of air (arrow A1) in the engine 12 as will be understood by one of ordinary skill in the art. The combustion of the fuel 25 generates exhaust gas (arrow B) which is subsequently passed through an exhaust manifold or conduit 47 in an exhaust system 11 is drained. By burning the fuel 25 energy released generates a torque or torque at an input element 13 of the transmission 14 , The gear 14 in turn transmits the torque from the engine 12 to an initial element 15 to the vehicle 10 by means of a set of driving wheels 18 drive.

The system 11 cleans it during the combustion of the fuel 25 generated exhaust gas (arrow B) and prepares it and includes as described below an oxidation catalyst (OC) 33 , a Selective Catalytic Reduction Catalyst (SCR) 43 and a particle filter (PF) 40 , The term "cleaning" as used herein refers to the removal of suspended particle aerosols or suspended particulate matter from the exhaust (arrow B), and therefore the system 11 configured to exhaust (arrow B) through the PF 40 to lead and lead. The PF 40 may be configured as a ceramic foam, metal mesh, granulated alumina, or other suitable material or other suitable combination of materials. The exhaust gas (arrow B) may also be removed using optional aftertreatment components (ATH). 29 are cleaned, which are formed as needed for receiving and / or removing other compounds from the exhaust gas (arrow B).

The term "treatment" as also used herein also refers to the control and / or regulation of the temperature of the exhaust gas (arrow B) at various points in the system 11 , For this purpose, the PF 40 with the OC 33 connected or integrally formed with the OC 33 with an external fuel injector device or an external injector 71 communicating as needed to delivering a controllable amount of fuel 25 in the OC 33 serves. In the OC 33 becomes the fuel 25 burned to thereby provide sufficient levels of heat to regenerate the PF 40 to create.

Ie. the OC 33 acts in the presence of a controlled temperature of the exhaust gas (arrow B) to oxidize, burn or otherwise eliminate any hydrocarbons introduced into the exhaust stream or flow. This sees a sufficient temperature value in the PF 40 for oxidizing a particulate material released from the PF 40 downstream of the OC 33 was held back. The PF 40 is thus kept relatively free of possibly clogging particulate matter, which otherwise affects the performance of the vehicle 10 could affect.

Between the OC 33 and the PF 40 is a conventional SCR 43 positioned. The SCR 43 is an apparatus or apparatus of the type known in the art for selective catalytic reduction, which can serve as by-products using an active catalyst for converting nitrogen oxides or NOx gases to water and nitrogen. The SCR 43 may be configured as a ceramic carrier or ceramic honeycomb structure, as a plate structure or other suitable design.

Regardless of the particular configuration or design of the SCR 43 is the SCR 43 a relatively large thermal mass in the system 11 between the OC 33 and the PF 40 is positioned. To the known thermal mass of the SCR 43 Therefore, a calibrated time delay or delayed temperature response is introduced when the exhaust gas slowly crosses the SCR 43 heated. Using the inlet temperature at the PF 40 as the primary feedback variable for controlling the exhaust gas temperature in the system 11 conventionally, the occurrence of a temperature overshoot in the OC 33 and the SCR 43 increase significantly. To minimize the occurrence of such overshoot, the system includes 11 Therefore, an electronic control device or a control unit 20 with a temperature optimization algorithm or method 100 , The system 11 can be a pair of maps or lookup tables 19A . 19B which are described below with reference to 2 and 3 to be discribed. Instead of the lookup tables 19A . 19B from 1 can the system 11 alternatively, if desired, include one or more curves (not shown) and / or a scalar calibration function or other suitable functions, which will also be described below.

The control unit 20 can be configured as a digital general-purpose computer or as a proportional-integral-derivative (PID) control device, which generally comprises a microprocessor or main processor (CPU), a read only memory (ROM), a random access memory (RAM), an electrically programmable read only memory (EPROM) , a high-speed clock generator, analog-to-digital (A / D) circuits and / or digital-to-analog (D / A) circuits, and input / output circuits or devices and suitable signal conditioning and buffer circuits. The procedure 100 and all required reference calibrations are in the ROM in the controller 20 are stored and readily executed to provide the respective functions described below with reference to FIG 2 and 3 are described.

The control unit 20 receives from different temperature sensors 21A -D, in different places in the system 11 are positioned, including the sensor 21B directly downstream of the OC 33 and the sensor 21C directly upstream of the PF 40 , Input signals, the sensors 21A -D for detecting, measuring or otherwise determining a temperature of the exhaust gas (arrow B) at various positions or locations in the system 11 serve.

In detail, the sensor 21A near the engine or the inlet side of the OC 33 positions and measures or detects an inlet temperature into the OC 33 , This temperature is _hereinafter abbreviated as T _{OC_IN for} the sake of simplicity. The sensor 21B detects an outlet temperature of the OC 33 This temperature is _hereinafter abbreviated as T _{OC_OUT for} simplicity. The sensor 21C detects an inlet temperature to the PF 40 This temperature is _hereinafter abbreviated as T _{PF_IN for} simplicity is. Finally, the sensor detects 21D an outlet temperature from the PF 40 This temperature is referred to herein as T _{PF_OUT} . These temperature signals are for use by the method 100 from 3 each through the sensors 21A -D to the controller 20 transferred or forwarded by these there. The control unit 20 is synonymous with the engine 12 in conjunction to obtain additional signals representing the operating point of the motor 12 determine, for example, throttle position, value or percentage (Th%), engine speed (N), accelerator pedal position, fueling amount, requested engine torque, etc.

With reference to 2 describes a representative series of courses 60 in general, an exemplary temperature relationship between the OC 33 and the PF 40 of the vehicle 10 , in the 1 are shown. The Y-axis includes predetermined or calibrated values, including but not necessarily limited to: a calibrated temperature peak in the OC 33 that as the line 80 or _{TOC, MAX is} shown; a desired temperature or setpoint temperature of the OC 33 that as the line 79 or _{TOC, T is} shown; and a desired temperature or setpoint temperature of the PF 40 that as the line 78 or _{TPF, T is} shown.

The X-axis represents time in 2 abbreviated as (t). The course 74 represents the actual or measured inlet temperature of the PF 40 ie, T _{PF_IN} , that of the sensor 21C from 1 is determined or measured. The history 72 sets the outlet temperature of the OC 33 ie, T _{OC_OUT} , from the sensor 21B from 1 is determined or measured. To the inlet temperature of the PF 40 raise, ie T _{PF_IN} from point 90 of the course 74 , ie from a height at which the course 74 initially to a point 91 plateaus, or the height of the line 78 shown calibrated value, ie T _{PF, T} , includes the method 100 from 3 balancing the known thermal mass of the SCR 43 and thus controlling the course 74 ie the controlled outlet temperature of the OC 33 or T _{OC, OUT} from 1 , in an area that is generally shaded by the area 75 is displayed, up to a calibrated upper limit, or a calibrated maximum, or T _{OC, MAX} passing through the line 80 is shown.

With reference to 3 together with the vehicle 10 from 1 the procedure begins 100 at step 102 that's every step of the way 102A . 102B and 102C includes. At step 102 are a set of predetermined operating values of the vehicle 10 measured, detected, calculated or otherwise determined and temporarily in the control unit 20 saved. Such values may be at different locations in the vehicle 10 be measured, for example, by measuring an amount of fuel or a throttle percentage (Th%) of the throttle 70 at step 102A and a rotational speed (N) of the engine 12 at step 102B , At step 102C For example, a calibrated integer value (CAL #) may be selected depending on the corresponding arrangement position of a desired assigned value as in step 104 will be described below. Typically, at step 102C an integer known to be the inlet temperature of the PF 40 is selected, although other temperature values, and thus other corresponding disposition positions, may be selected within the scope of the invention. Then the procedure moves 100 to step 104 in front of each of the steps 104A -C includes.

At step 104 includes the method 100 selecting a corresponding predetermined or calibrated value or setpoint for both the OC outlet temperature and the PF inlet temperature. step 104 can be realized by various means, for example by accessing a look-up table, for example the look-up tables 19A . 19B from 1 which refer to an arrangement by calculation using various functions described above and / or by other suitable means. At step 104A for example, the one at step 102A determined throttle valve value (Th%) and the at step 102B determined engine speed (N) as inputs to a first map or a look-up table 19A used that the OC 33 corresponds, and the resulting value becomes step 112 overtop. At step 104B become the values from the steps 102A respectively. 102B in a second map or look-up table 19B entered the PF 40 corresponds, and the resulting value becomes step 106 transfer. Finally, at step 104C the calibrated value (CAL #) of step 102C entered into an array, and a corresponding measured temperature value for an inlet or outlet of the PF 40 and the OC 33 becomes the steps 106 and 107 transfer. Then the procedure moves 100 to the steps 106 . 107 and 112 in front.

At step 106 is the by means of the arrangement in step 104C The measured value subtracted from the value subtracted from the PF map at step 104B was determined to determine an error value or error term, which then moves to step 108 forwarded or transmitted. For example, as described above, a first temperature set point for the OC outlet temperature may be selected, while a second setpoint temperature value may be selected for the PF inlet temperature. After the temperature in the exhaust stream stabilizes, for example, by allowing a timer to expire or a predetermined interval The mathematical difference between the measured PF inlet temperature and its calibrated second temperature setpoint may be calculated as an error term. Then the procedure moves 100 to step 108 in front.

At step 107 becomes out of the order at step 104C The selected value is compared to a calibrated range or set of allowable max / min values to determine if the selected value falls within the upper and lower limits of the range, ie [Range O, Range U]. If the value of step 104C is less than the upper range value (range O) and greater than the lower range value (range U), the method includes 100 starting a timer to elapse a predetermined interval. step 108 provides a sufficient buffer that the temperature effect of the relatively large thermal mass of the SCR 43 compensates (see 1 ).

Alternatively, the thermal mass of the SCR 43 be considered as a function of exhaust flow, with different "wait" times are used for different engine operating points. Analogously, the look-up tables include 19A . 19B Data showing an expected temperature drop above the SCR 43 consider or compensate. After the timer has expired, or other alternative steps that equalize the thermal mass have been completed, step S5 107 an activation signal or switching signal (arrow S) to step 110 forwarded or transmitted.

At step 108 will be the error term of step 106 filtered to take a moving average of the error values so as not to unnecessarily respond to large but transient error values. step 108 may include, but is not limited to, passing the error term through a first-order filter, calculating a moving average of error terms, etc. In this way, the system stability can be further optimized. The filtered error value then becomes step 110 transmitted.

At step 110 becomes a constant value of zero continuously to step 112 forwarded or transmitted until the switching signal (arrow S) of step 107 Will be received. When the switching signal (arrow S) is received, the at step 108 determined error term to step 112 forwarded or transmitted.

At step 112 becomes the value of step 104A which was selected as described above from an OC map or a look-up table to which error term added from step 110 was transmitted. The total value of an outlet setpoint temperature of the OC 33 or T _{OC, T} (see line 79 from 2 ), then becomes step 114 transmitted.

At step 114 becomes the outlet set temperature of the OC 33 or T _{OC, T} with a calibrated maximum for the OC 33 or T _{OC, MAX} compared to that of the line 80 from 2 equivalent. The procedure 100 then involves transmitting the minimum value of the values T _{OC, T} and T _{OC, MAX} . This in 2 as a course 74 The value shown is the final temperature of the OC 33 , in the 3 as T _{OC, F is} shown. This value then becomes a suitable part of the controller 20 or forwarded to another control device that determines the percentage of fuel 25 from 1 that controls to the external injector 71 or diverted by cylinder injectors (not shown).

A general example is illustrated with a situation where the calibrated maximum OC temperature or T _{OC, MAX is} equal to 700 ° C and the first temperature set point of step 104A is equal to 650 ° C. An exemplary placement value of 2 at step 102 can in an arrangement at step 104 correspond to a measured PF inlet temperature. This value, _hereinafter abbreviated as T _{PF_IN} , is equal to 650 ° C for purposes of the present example. A desired or calibrated second temperature set point for the PF inlet temperature may then be determined at step 104B be selected or determined at 648 ° C. In this example, step 106 then generate a value of (T _{PF_IN} setpoint 2) or (650 ° C-648 ° C) = 2 ° C. Therefore, 2 ° C is the one from step 106 transmitted error term.

If the at step 104C determined value of the temperature measurement, here 650 ° C, at step 107 within a certain range [range O, range U], the error value of 2 ° C at step 108 through a first order filter or other suitable filter and at step 110 be filtered by a switching or logic gate before going to step 104A determined first temperature setpoint or 650 ° C is added in this particular example. The output value or (650 ° C + 2 ° C) = 652 ° C is set as the OC outlet set temperature or T _{OC, T} , then compared to a calibrated maximum value, for example, 700 ° C. The minimum of these two values, ie 652 ° C, then becomes the controller 20 as value TOC, F (see line 72 from 2 ) transmitted. As will be understood by one of ordinary skill in the _art, the value T _{OC, F may be} from the controller 20 be used to a corresponding volume or mass flow of the injection by means of the external injector 71 or the cylinder injectors (not shown) required fuel 25 to calculate, retrieve or otherwise determine the OC 33 to burn to reach the final temperature T _{OC, F.}

While the best methods to perform The person skilled in the art to which this invention is directed will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.

Claims (10)

Method for controlling a temperature of an exhaust gas from a vehicle engine during a regeneration of a particulate filter (PF) in a vehicle, the one oxidation catalyst (OC), a catalyst for selective catalytic reduction (SCR) and the PF, the method comprising: To adjust a concentration of hydrocarbons in the exhaust gas to thereby to achieve a first temperature setpoint; Determine a second temperature setpoint corresponding to a PF inlet temperature; Subtract the second temperature setpoint from a measured PF inlet temperature, thereby calculating an error term; Add the error term to the first temperature setpoint thereby to set an OC outlet set temperature to investigate; and To run a tax measure while the regeneration of the PF, thereby ensuring that an OC end temperature not a maximum exceeds the OC outlet setpoint temperature and a calibrated OC outlet high temperature. The method of claim 1, further comprising Determining the first temperature setpoint using an OC outlet temperature. The method of claim 1, further comprising Filter the error term before adding the error term to the includes first temperature setpoint. The method of claim 3, further comprising Introduce a calibrated time delay before calculating the error term, wherein the calibrated delay sufficient to compensate for a known thermal mass of the SCR. Method according to claim 1, wherein the determining of the first and second temperature setpoints, both of the first and second temperature setpoints from a corresponding one Lookup table, wherein each of the lookup tables by a plurality of predetermined operating values of the engine is indicated, in which the plurality of predetermined operating values of the engine preferably include: a throttle position, an accelerator pedal position, a Fuel supply amount, a required engine torque and a Speed of the motor. The method of claim 1, further comprising: to compare the measured PF inlet temperature with a calibrated range permissible PF inlet temperatures; Add of the error term to the first temperature setpoint, only if the measured PF inlet temperature within the calibrated range of permissible PF inlet temperatures lies; and Use the calibrated OC maximum temperature as the OC target temperature, only if the measured value is not within the calibrated range permissible PF inlet temperatures lies, being doing a tax measure Preferably, controlling includes a lot of fuel from the OC the regeneration of the PF is burned. A method of controlling a temperature of an exhaust gas from an engine during regeneration of a particulate filter (PF) in a vehicle having an oxidation catalyst (OC), a selective catalytic reduction (SCR) catalyst, and the PF, the method comprising: selecting one first temperature setpoint from a first look-up table, wherein the first temperature setpoint corresponds to an OC outlet temperature; Selecting a second temperature setpoint from a second lookup table, wherein the second temperature setpoint corresponds to a PF inlet temperature; Measuring an actual PF inlet temperature; Subtracting the second temperature setpoint from the actual PF inlet temperature to calculate an error term; Filtering the error term to thereby compensate for a known thermal mass of the SCR; Adding the error term to the first temperature setpoint to determine an OC outlet setpoint temperature; and controlling an actual OC outlet temperature during regeneration of the PF such that the actual OC outlet temperature does not exceed a maximum OC outlet setpoint temperature and a calibrated OC outlet maximum temperature, wherein filtering an error term is one of the following comprises: passing the error term through a first order filter and calculating a moving average of a plurality of the error terms; and wherein calculating the first and second OC outlet target temperatures comprises: measuring at least one engine value selected from the group consisting of a throttle position, an accelerator pedal position, a fuel supply amount, and a requested engine torque; Measuring a rotational speed of the engine; and Selecting a calibrated OC temperature from a look-up table indexed by the at least one engine value and the speed of the engine. Device for controlling a temperature of an exhaust gas in an exhaust system of a vehicle engine during a regeneration of a Particulate filter (PF), wherein the exhaust system is an oxidation catalyst (OC), a catalyst for selective catalytic reduction (SCR) and the PF, wherein the device comprises: several sensors, each for Measuring a temperature in a different part of the exhaust system serve; and a control unit, this is an algorithm, a lookup table of OC outlet temperatures and having a look-up table of PF inlet temperatures, wherein each of the look-up tables is characterized by a plurality of engine operating values is indexed; the algorithm being designed so that it is an OC outlet setpoint temperature calculated using data from each look-up table, wherein the target OC outlet temperature is a thermal mass of the SCR balances; and where the algorithm is an actual OC outlet temperature during Regeneration of the PF to the lower value of OC outlet target temperature and calibrated OC outlet maximum temperature. Apparatus according to claim 8, wherein the algorithm a computational difference between one from the PF lookup table selected Temperature setpoint and a measured PF inlet temperature calculated and the difference to another from the OC lookup table selected Temperature setpoint added to thereby increase the value of the OC outlet setpoint temperature determine. A method according to claim 8 or 9, which comprises a with a supply for Fuel and the controller comprising a related fuel injector; wherein the controller for calculating a Amount of fuel used to generate the lower value of OC outlet setpoint temperature and calibrated OC outlet high temperature required and arranging a supply of the calculated amount of fuel serves to the fuel injector.